Is Mr. Sun Yat-sen a descendant of Sun Quan?

No.

Sun Yat-sen (November 12, 1866 - March 12, 1925) was famous for his literary works and his nickname was Zai Zhi. His nickname was Rixin and Yixian. His childhood name was Emperor Xiang, and his pseudonym was Zhongshan Qiao. He is the pioneer of China's modern national democratic revolution, the great forerunner of China's democratic revolution, the founder of the Republic of China and the Chinese Kuomintang, the advocate of the Three People's Principles, and the founder of the "Five Powers Constitution". He was the first to raise the banner of thorough anti-imperialism and anti-feudalism, "initiating peace and ending two thousand years of feudal monarchy."

Sun Yat-sen was born into a peasant family in Cuiheng Village, Xiangshan County, Guangdong Province (now Zhongshan City). In his youth, he was influenced by the struggle tradition of the Guangdong people and yearned for the cause of the Taiping Rebellion against the Qing Dynasty. He called himself "the second Hong Xiuquan". In 1905 (the 31st year of the reign of Emperor Guangxu), the China Tongmenghui was established. On October 10, 1911 (the third year of Xuantong), the revolutionaries in the New Army contacted secretly and decided to revolt that night. After the Revolution of 1911, he was elected as the interim president of the Republic of China (term January 1, 1912 - April 1, 1912). Sun Yat-sen died in Beijing on March 12, 1925. On June 1, 1929, according to his last wish, he was buried at the Sun Yat-sen Mausoleum in Zijin Mountain, Nanjing. In 1940, the Nationalist Government issued an order to the whole country, honoring him as the "Father of the Republic of China".